Underhood Ammeter Bypass

Mike66Chryslers

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Whatever you do, don't do this. :eek: This rewiring job was on a '51 Merc advertised in FB Marketplace. The seller claims that the previous owner paid someone $1500 to rewire the car for 12V to use with a Chevy 305 that they put in it. It looks like the inside of a pinball machine.

upload_2021-11-24_14-49-22.png
 

Bucket

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Use a fusible link if its anything under 120 amps. **** ON what the auto parts liars tell you. They're just out to sell you crap, and they KNOW NOTHING! If you've got an alternator between 75 and 100 amps, and can keep your wire length under 6 feet, use #8 AWG, w 12 AWG fusible link wire, 6 inches, ideally between the battery + post and the charging lead from your alternator.
The thing is they didn't try to sell me anything else .
These blokes are all into cars and i have have known them for 20 + years.
They told me they can't even buy fuseable links or wire anymore .
 

Bucket

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What are "ADR rules"? The only thing Google turned up was Alternative Dispute Resolution. Something to do with your insurance company?
If fusible links are what your car came with originally, why would there be a problem retaining the OEM-style solution?
You could also consider a MIDI/AMI fuse, AMG/MEGA fuse or similar high-current slow-blo strip fuse. MIDI are available in sizes up to 200A. If a circuit breaker is not "slow-blow", I would think a MIDI fuse sized to the max output of your alternator would be a better option. It could handle short durations of max output, but sustained max output would indicate a problem and the fuse would blow.
Thanks for this information .
The car is a 1961 Newport , i am still trying to figure out the alternator output .
The alternator has 2095191 on the front and twin pulleys .
From what i can find this may have been a 60 amp .
I have no idea if it has been re manufactured .
From the wiring diagram in the FSM i can not see any fuseable links in the wiring loom .
I may be missing something .
 

Gerald Morris

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The thing is they didn't try to sell me anything else .
These blokes are all into cars and i have have known them for 20 + years.
They told me they can't even buy fuseable links or wire anymore .

Buy the WIRE, cut it to length, and make your own. Very easy. I certainly have NO TROUBLE obtaining fusible link wire. I suppose, given your location, things MAY DIFFER DOWN UNDER. Alas! I suppose you can order from the States, unless the Gov would BUST you for it? Would they go THAT FAR?

If so, I say, its time to emigrate. I recall 30 yrs ago, I thought of heading your way, BUT THEN, I researched certain trends in Commonwealth countries, and decided to stay put, bad as that is. Bureaucrats amplified by microprocessors are really screwing the planet up, though they're hardly ALONE in THAT!

Domine, miserere nobis!
 

Bucket

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What are "ADR rules"? The only thing Google turned up was Alternative Dispute Resolution. Something to do with your insurance company?
If fusible links are what your car came with originally, why would there be a problem retaining the OEM-style solution?
You could also consider a MIDI/AMI fuse, AMG/MEGA fuse or similar high-current slow-blo strip fuse. MIDI are available in sizes up to 200A. If a circuit breaker is not "slow-blow", I would think a MIDI fuse sized to the max output of your alternator would be a better option. It could handle short durations of max output, but sustained max output would indicate a problem and the fuse would blow.
The local parts shop has a 60amp Midi fuse .
I have seen some other ones advertised as 1 way (direction?)
Are they all 1 way and would this make a difference ?
 

Gerald Morris

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A one way midi fuse would direct over-current protection down to the elements, but not the current source. Midi fuses WERE designed as replacements for fusible links, so if you indeed can't get on the road any other way, then a midi fuse would probably be your closest substitute for them. Look at maxi-fuses also.

I actually tried the latter in place of a fusible link 5 years ago, when I had what I thought were circuiting troubles. It turned out, I had a broken motor mount, and when I accelerated, the charging stud from the alternator would ground and short circuit! The fuses blew out TOO fast, even after replacing the motor mount, I found any sudden demand on the charging system had a way of popping maxi-fuses. This is why I took such a vehement tone at first regarding the suggestion from your mates at the auto supply.

Design for worst case scenarios, and upgrade your charging circuit to #8 wire, with 80 amp midi fuses, and you might do well.
 

USSMOPAR

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1972 Chrysler station wagons with the trailer towing package had a factory ammeter bypass. I owned a 9 passenger, brown, dual air, cruise control, pwr antenna, am fm, grab handles, bumper guards, cornering lights, 400, tinted glass, 3.23 sure grip 8-3/4.
 

cbarge

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1972 Chrysler station wagons with the trailer towing package had a factory ammeter bypass. I owned a 9 passenger, brown, dual air, cruise control, pwr antenna, am fm, grab handles, bumper guards, cornering lights, 400, tinted glass, 3.23 sure grip 8-3/4.
Police cars with big alrernators also bypassed the bulkhead connector
 

Ross Wooldridge

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My 66 Canadian 440 4-speed Monaco was special order built to police specs, and has a factory bulkhead bypass. Also had the high output alternator and adjustible regulator mounted on the inner fender...
 

Yeahrightgreer

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The local parts shop has a 60amp Midi fuse .
I have seen some other ones advertised as 1 way (direction?)
Are they all 1 way and would this make a difference ?

If you can, I would just order it in from the states like Gerald mentioned. Easiest solution in my opinion. Unless it is illegal to bring in for some reason. It's very cheap and readily available here in the states.
 

cbarge

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Did a video of the bypass.
I am not good with the camera so my apologies in advance and I yet have to learn how to edit on youtube.
 

CBODY67

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(Edit the video on the camera or computer before posting it to YouTube?)
 

Wilkiethegrid

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Thanks for the great contribution.
If I were to use a fuse what Amp rating would be most appropriate?
I have a 63 Dodge 880 Custom 361cid with AC, power windows and seats. 33k original miles. I don't know what the output of my alternator is.
 

cbarge

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Thanks for the great contribution.
If I were to use a fuse what Amp rating would be most appropriate?
I have a 63 Dodge 880 Custom 361cid with AC, power windows and seats. 33k original miles. I don't know what the output of my alternator is.
I do not use fuses in this particular application. As mentioned before, fusible links are capable to handle any spikes whereas a fuse will blow.
Fusible links are designed to burn first before anything else...Kinda like taking one for the team so to speak! Lol!
 

HOT FURY

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It took longer to do the thread compared to the wiring,LOL!!
But I cannot stress enough how important this 15 minute job is .
What it does is piggy back on the ammeter circuit. This wire takes 50% of the load away from the ammeter itself.
We all know the ammeter gauge is the achilles heel in our beloved old Mopars.
The fusible link is a safeguard should the alternator short out and not burn the dash or car to the ground.

You wil notice that the ammeter gauge will not swing as crazy as before and will not read 100% accurately.
But still works--until is does short out but the car will still function normally on a day to day basis.
An option is install an afermarket volt gauge.
Simpy hook it to a switched 12 volt source and ground it to body. done.

In laymans terms the Red wire at starter relay goes through the bulkhead and eventually to the ammeter gauge--which is hot all the time.
Hot I mean live as in anything that is run by battery no ignition key needed (headlights,hazards,dome light lighter,etc)
The black wire on the ammeter goes to the ignition switch which as you know powers anything that needs the key on.
So when the ammeter shorts out you have NOTHING!
This simple little addition is worth its time,trust me.

I cannot take credit for this mod.I first read about it in MOPAR ACTION
20 years ago writen by Richard Ehrenberg.
Hope this helps.
Any guess as to what size inline fuse I would use for this instead of a fusible link?
 
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